Printer

ABSTRACT

A printer is provided with a plurality of print hammers, each of which is maintained in a rest position engaging a deformed elastic body. A magnetic circuit is provided for selectively maintaining each of said print hammers in said rest position and for selectively releasing said print hammer to effect printing. The magnetic circuit consists of a first portion including a portion of said print hammer and a second portion including a release coil, the first and second portions being connected in parallel with a permanent magnet so that said print hammer is released from its rest position by exciting the release coil in a direction such that the magnetomotive force applied to said print hammer to hold said print hammer in position is decreased, the displacement of the print hammer being the product of the release of the energy of the elastic body.

United States Patent 1191 Gomi Oct. 22, 1974 PRINTER W Primary Examiner-Robert E. Pulfrey [75] Inventor. Yoshlfuml Goml, Chino, Japan 7 Assistant Examinere Edward M. Coven 1 Assignees: Kabllshiki Kflisha Sllwa SeikOSha, Attorney, Agent, or FirmBlum, Moscovitz, Friedman Chuo-ku, Tokyo; Shinshu Seiki & Kaplan Kabushiki Kaisha, Suwa-shi, Natano-ken, both of Japan [57] ABSTRACT [22] Flled: 1972 A printer is provided with a plurality of print ham- [21] App], N0; 319,438 mers, each of which is maintained in a rest position engaging a deformed elastic body. A magnetic circuit is provided for selective] maintainin each of said [30] Forelgn Apphcauon Pnomy Data print hammers in said rest position and for selectively Dec. 29, 1971 Japan; 46-728 releasing d print hammer to effect printing. The DEC. 29, 1971 Japan 46-729 magnetic circuit consists of a first portion including a portion of said print hammer and a second portion in- U-S- eluding a release coil the first and econd portions Int. 0 1 being connected in parallel a permanent magnet of Search C so that said print hammer is released from its rest position by exciting the release coil' in a direction such References Clted that the magnetomotive force applied to said print UNITED STATES PATENTS hammer to hold said print hammer in position is de- 3.049.990 8/1962 Brown et al 101/93 c creased, the displacement of the Print hammer being 3,460,469 8/1969 Brown et al 101/93 c t product of the release of the gy of the elastic 31,59,238 4 1972 Grifiing ..101/93 C X body. 3,675,172 7/1972 Petusky 101/93 0 3,707,122 12 1972 Cargill 101/93 0 6 clalms, 3 Drawmg Figures PAIENIEDUU 221924 mums FIG /0 PRINTER BACKGROUND OF THE INVENTION This invention relates to a control mechanism for the print hammer of a printer, and particularly relates to a control mechanism for such print hammers wherein the print hammer is displaced by the stored energy of an elastic body upon the application of a print command.

In the art, various hammer mechanisms have been proposed for high-speed mechanical printers used as the output portion in information managing devices. Many such printers are of the flying type wherein the characters to be printed are carried by drum, a belt or a chain which is continuously rotated, printing being effected by striking a recording device such as paper against the character to be printed by means of a hammer, wituout interrupting the rotation of the character carrier. In a high-speed printer, printing speed, and therefore the speed of movement of the character carriers is extremely fast. This requires rapid and precise movement of the hammer in order to insure that the hammer sqarely strikes the correct character, thereby insuring accurate and clear printing.

The prior art flying printers generally utilize the attractive forces of an electromagnet to displace the hammer. Such arrangements generally require the use of a lever to transmit the energy generated by the attraction of the electromagnet to the hammer. The energy required for the displacement of said lever, as well as for the movement of an attractive plate or other mechanism is wasted. The large energy requirement necessitates the application of 5 amperes or more of current per column, as well as the expenditure of relatively substantial periods of time for the carrying out of the printing operation. Where a printer has 130 columns, 700 amperes or more of current is required should all of the columns be actuated at the same time. This results not only in the requirement for a largescale power device, but also results in the generation of substantial heat. By providing a hammer mechanism wherein the hammer can be controlled by a small current, the foregoing deficiencies can be avoided.

SUMMARY OF THE INVENTION Generally speaking, in accordance with the invention, a printer is provided having a print hammer displaceable between a rest position and a printing position, an elastic body maintained in a deformed state by said print hammer at said rest position, and magnetic circuit control means for retaining said print hammer at said rest position and for selectively releasing said print hammer upon command. Said magnetic circuit control means includes a first portion including a portion of said print hammer, a second portion including a release coil and a permanent magnet connected'in parallel with said first and second portions of said magnetic circuit control means. Said magnetic circuit control means is adapted so that said print hammer is normally retained at said rest position by the magnetomotive force applied thereto, said magnetomotive force being decreased upon the excitation of said release coil, said print hammer being displaced from said rest to printing positions by the stored energy of said elastic body.

Said first and second portions of said magnetic circuit control means may be connected to said permanent magnet through a magnetic saturation portion.

Accordingly, it is an object of this invention to provide a printer wherein a hammer is held at a rest position by the magnetic force generated by a permanent magnet while storing energy in an elastic body such as a spring.

Another object of the invention is to provide a hammer control mechanism for a printer which may be actuated by a relatively small control current.

Still another object of the invention is to provide a printer having a plurality of hammers controlled by a magnetic circuit control device, the control of each of said hammers being effected without interfering with the operation of the other of said hammers.

Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification and drawings.

The invention accordingly comprises the features of construction, combinations of elements, and arrangement of paits'which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.

BRIEF DESCRIPTON OF THE DRAWINGS For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings, in which:

FIG. 1a is a partially sectioned side elevational view of the operative portion of one column of a printer in accordance with the invention;

FIGS. 1b and 1c are side elevational views of second and third embodiments of the magnetic circuit control device in accordance with the invention;

. FIG. 2 is an electrical equivalent circuit of the magnetic circuit of FIG. 1a;

FIG. 3 is a graphical representation of the permeance coefficient of the permanent magnet of FIG. la;

FIG. 4 is a partially sectioned side elevational view of a fourth embodiment of one column of the printer in accordance with the invention;

FIG. 5 is a fragmentary front and a fragmentary side elevational view of three columns of the magnetic circuit control means of FIG. 4; and

FIG. 6 is a partially sectioned side elevational view of the magnetic circuit control device in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. la, one column of a multicolumn printer is depicted. The printer includes a hammer I mounted for longitudinal displacement on suspending springs 5. A magnetic circuit for the control of the displacement of said hammer is provided consisting of yokes 2 and 2' having attractive faces 2a and 2'a respectively for holding hammer l in a rest position, as illustrated in FIG. 1a. The magnetic circuit also includes a permanent magnet 3 and a release coil 4 mounted on an arm of said magnetic circuit extending between yokes 2 and 2so as to be in parallel with attractive faces 2a and 2'a and the portion of hammer 1 therebetween. The rear end of hammer l is provided with a contact maker 9 which engages and compresses a coil spring 6 at the rest position of the hammer illustrated in FIG. 1a.' Said coil spring is positioned by spring guide 7 and is retained between contact maker 9 and fixing plate 8. The stroke of hammer l is limited by stopper 10 which is engaged by contact maker 9 upon the release of the hammer in the manner described below. Stopper 10 also serves as part of a reset mechanism (not shown) to reengage hammer 1 against attractive faces 2a and 2'a and compress spring 6 when said stopper is displaced in the direction of the arrow to the position shown in dashed lines in FIG. la. Printing is effected by engagement of the front end of hammer 1 against recording paper 12 to force said recording paper against an ink ribbon 13 and the surface of a character-carrying drum 11. Drum 11 is continuously rotating and has a series of characters circumferentially spaced in alignment with the column represented by FIG. la. In practice, one such circumferential array of characters would be provided for each column of the printer. The characters may consist of symbols, numbers or letters as desired.

FIGS. lb and 1c depict two alternative structures for the magnetic circuit control device, like reference nu-. merals being applied to like elements depicted in FIG. 1a.

The operation of the arrangement in accordance with the invention is best understood by reference to FIG. la, which is depicted at the rest position of the ham mer. At this position, hammer l is held by the attractive faces 2a and 2'a of yokes 2 and 2' due to the holding force generated by the magnetic flux loop i including said yokes and permanent magnet 3. The holding force applied to hammer'l is sufficient to overcome the driving force of spring 6, and is further sufficient to hold said hammer in position despite the influence of changes in temperature, vibration and the like. The operating point of the permanent magnet at the rest position is determined by the entire magnetic circuit inclugind the hammer portion and the release coil portion. The permeance coefficient (Bd/Hd) will be at point a of the graph shown in FIG. 3.

As noted above, character carrying drum 11 rotates at a predetermined speed. When the selected character approaches alignment with hammer l, a signal is applied to release coil 4. The direction of the signal applied to the release coil is such as to increase the quantity of magnetic flux of the magnetic flux loop ii. As shown in the graph of FIG. 3, the magnetomotive force U is applied to the permanent magnet in the direction shown in FIG. 3 so that the operating point of the permanent magnet is moved to the position b.

An equivalent circuit of the arrangement -is depicted in FIG. 2, wherein Hdl represents the magnetomotive force of the permanent magnet, U represents the magnetomotive force generated by release coil 4, r represents the reluctance in the release coil portion,'and R is the reluctance in the hammer holding portion of the magnetic circuit. When the magnetomotive force generated by release coil 4 (U) is applied, the magnetomotive force l-Idl of the permanent magnet is lowered. Specifically, the magnetomotive force between points c and d on FIG. 2 is lowered. Accordingly, the magnetic flux i flowing through the hammer holding portion of the magnetic circuit is decreased and the holding force is lowered. When the holding force is lowered to a level below that required to balance the force of driving spring 6, the hammer is separated from attractive faces and 2'a and is driven in the direction of the character to be imprinted. Spring 6 continues to apply hammer l with energy for printing until the stop portion of contact maker 9 engages stopper 10. After the contact maker 9 is stopped by stopper 10, the character is struck by the kinetic energy stored in the hammer. The return of the hammer is achieved by a hammer return mechanism (not shown). Specifically, hammer l is attracted to the attractive faces 2a and 2'a of yokes 2 and 2 respectively due to the magneticforce of the permanent magnet 3 when stopper 10 is displaced in the direction of the arrow shown in FIG. la. Of course, at this time, current would not be flowing through release coil 4. Stopper 10 is then returned to its initial position and -the hammer is ready to print the next character. In this manner, each line of printing is effected. Of course, paper 13 and ribbon 1 2 would be advanced after each line is printed. I

The precise positioning of the two magnetic circuit portions is subject to selection as shown in FIGS. la, lb and 10. However, all of these embodiments have the following points in common:

a. the hammer does not obtain the print energy directly from the electromagnetic device, but rather, such energy is obtained from energy stored in a spring. The release coil merely acts as a trigger for the magnetic circuit.

b. the hammer is held at the rest position by the magnetic force of the permanent magnet until release.

c. the magnetic circuit consists of a holding portion for the hammer, a release coil portion and a permanent magnet, the hammer hold portion and release coil portion being connected in parallel with said permanent magnet.

d. the release of the hammer from the hammer hold portion is achieved by exciting said release coil in a direction such that the magnetomotive force of the permanent magnet is lowered.

Experiments with the arrangement in accordance with the invention has revealed that the hammer mech anism can be controlled with a very small current, of the order of I00 ampere-turns os less per column and per operation. The arrangement in accordance with the invention can be applied as the hammer for serial printers and line printers which print every character. Since power consumption is very small, control of the hammer mechanism is readily achieved.

One problem with the arrangement depicted in FIGS. 1a, 1b and 1c, is that in the case of a line printer, wherein hammers for a large number of columns are provided, the action of one hammer may cause changes in the permeance coefficient Bd/Hd of the permanent magnet (the operating point of the permanent magnet), therefore affecting the operation of the other hammers. This defect is avoided by the construction of FIG. 4.

As in the case of the embodiment of FIGS. 1a, lb and lo, a hammer 21 is suspended for longitudinal displacement on springs 25 and is provided with a contact maker 29 which, at the rest position compresses a spring 26, spring 26 being retained in position by spring guide 28, which in turn is mounted on a fixing plate 29. The magnetic circuit is provided with a permanent magnet 23 and a pair of yokes 22 and 22', said yokes having attractive faces 22a and 22'a respectively. The magnetic circuit also includes a release coil 24 wound about a portion positioned in parallel relation to the hammer hold portion of the magnetic circuit. A continuously rotating print drum 31 bearing the characters to be imprinted is provided to effect imprinting on recording paper 33 by means of ink ribbon 32. The arrangement of FIG. 4 differs from the preceding arrangements principally in the provision of a region A of the magnetic circuit characterized by magnetic saturation, the parallel connection of the release coil portion of the hammer hold portion of said magnetic circuit being connected in parallel with permanent magnet 23 through said magnetic saturation region A.

The operation of the arrangement of FIG. 4 is more particularly understood by reference to FIG. 5 which depicts portions of three columns of the arrangement of FIG. 4, the subscripts representing each column. When the hammer is held at the rest position, magnetic flux from permanent magnet 23 flows in both loops of the magnetic circuit, namely the loops identified as i and ii. The magnetic flux in loop 1' is effectively utilized to hold the hammer in said rest position. Since region A saturates upon the application of magnetic flux thereto, the quantity of magnetic flux flowing through loop i is not changed upon slight changes in the magnetomotive force.

Although the operating point (magnetic field intensity) of the permanent magnet is changed due to changes in the reluctance of the magnetic circuit including said permanent magnet due to release of one or more hammers, this change in operating point of the permanent magnet does not affect the holding power of the other hammers.

When the selected character on the print drum approaches alignment with the hammer, release coil 44 is excited in the direction tending to increase the quantity of magnetic flux in magnetic flux loop ii so as to substantially decrease the magnetic flux flowing in magnetic flux loop 1'. This serves to release hammer 21 so as to displace said hammer to effect printing due to the energy stored in spring 26, as described above.

From the foregoing, it is apparent that if a magnetic saturation region is provided in the portion of the magneic circuit interconnecting the permanent magnet and the parallel-connected release coil portion and hammer-hold portion, the quantity of magnetic flux flowing through the hammer hold portion can be maintained constant despite slight changes in the operating point of the permanent magnet due to the influence of the operation of other columns of the printer. In effect, the holding force applied to the hammer is not influenced by the operation of the other columns, but is maintained constant. Further, the operation of release coil 24 is independent of the operation of the other columns, and additional current is not required to energize the release coil to effect release of the hammer.

FIG. 6 illustrates an alternate embodiment of the magnetic circuit control device in accordance with the invention wherein hammer 41 is retained against attractive faces 42a and 42 'a of yokes 42 and 42 respectively and the release coil 44 is connected in parallel with the hammer-hold portion of the magnetic circuit. The embodiment of FIG. 6 differs from the embodiment of FIG. 4 in that region B is dimensioned to define a magnetic saturation region. Either region A or region B may be so formed, or if desired, both regions may be so formed to define magnetic saturation regions.

From the foregoing it is apparent that the embodiments of FIGS. 4-6 may be operated with very low current and are particularly stable.

It will thusbe seen that the objects set forth above,

and those made apparent from the preceding descrip-' tion, are efficiently attained and, since certain changes may be made in the above constructions without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

What is claimed is:

1. In a printer having a plurality of print columns, each column having print hammers displaceable between a rest and a print position; a deformable elastic body maintained in a deformed condition by the associated print hammer at said rest position; improved mag netic circuit control means for selectively holding the associated hammer at a rest position and releasing same for displacement to a print position including a permanent magnet common to at least two of said columns, a first hammer-hold magnetic circuit portion including a portion of the associated print hammer, and a second release rfiagnridefimrpeimfigaertea with each print hammer including release coil means, said first and second magnetic circuit portions being connected in parallel to each other, said parallel connection being connected to said permanent magnet for receiving magnetic flux therefrom, each of said magnetic circuit control means being adapted to hold the associated hammer at said rest position and to release said associated hammer upon the application of a signal to the associated release coil means in a direction so as to decrease the magnetomotive force applied to the associated hammer, the energy stored in the associated deformed elastic body displacing the associated hammer from said rest position to said print position upon said decrease in said magnetomotive force.

' 2fA printer as recited in claim 1, wherein each said magnetic circuit control means includes a magnetic saturation region, said first and second magnetic circuit portions being connected in parallel through said magnetic saturation region with said permanent magnet.

.3. A printer as recited in claim 2, wherein each said first magnetic circuitportion includes yokes associted with a respective print hammer and having a pair of attractive faces, each said hammer including portions positioned for associated engagement against the attractive faces at said rest position.

4. A printer as recited in claim 2, each hammer having a respective stopper means positioned in the path of a portion of said hammer for stopping the displacement of said hammer at said print position.

5. A printer as reicted in claim 4, including a continuously moving character carrying means adapted to sequentially carry each of the characters to be printed through a position in operative registration with said hammers, said hammers being adapted to be carried into engagement with said character carrying means to effect printing after engagement with said stopper means due to the kinetic energy of said hammers means.

6. A printer as recited in claim 4, wherein said stopper means is displacable for returing said hammer to said rest position after printing. 

1. In a printer having a plurality of print columns, each column having print hammers displaceable between a rest and a print position; a deformable elastic body maintained in a deformed condition by the associated print hammer at said rest position; improved magnetic circuit control means for selectively holding the associated hammer at a rest position and releasing same for displacement to a print position including a permanent magnet common to at least two of said columns, a first hammer-hold magnetic circuit portion including a portion of the associated print hammer, and a second magnetic circuit pOrtion associated with each print hammer including release coil means, said first and second magnetic circuit portions being connected in parallel to each other, said parallel connection being connected to said permanent magnet for receiving magnetic flux therefrom, each of said magnetic circuit control means being adapted to hold the associated hammer at said rest position and to release said associated hammer upon the application of a signal to the associated release coil means in a direction so as to decrease the magnetomotive force applied to the associated hammer, the energy stored in the associated deformed elastic body displacing the associated hammer from said rest position to said print position upon said decrease in said magnetomotive force.
 2. A printer as recited in claim 1, wherein each said magnetic circuit control means includes a magnetic saturation region, said first and second magnetic circuit portions being connected in parallel through said magnetic saturation region with said permanent magnet.
 3. A printer as recited in claim 2, wherein each said first magnetic circuit portion includes yokes associted with a respective print hammer and having a pair of attractive faces, each said hammer including portions positioned for associated engagement against the attractive faces at said rest position.
 4. A printer as recited in claim 2, each hammer having a respective stopper means positioned in the path of a portion of said hammer for stopping the displacement of said hammer at said print position.
 5. A printer as reicted in claim 4, including a continuously moving character carrying means adapted to sequentially carry each of the characters to be printed through a position in operative registration with said hammers, said hammers being adapted to be carried into engagement with said character carrying means to effect printing after engagement with said stopper means due to the kinetic energy of said hammers means.
 6. A printer as recited in claim 4, wherein said stopper means is displacable for returing said hammer to said rest position after printing. 